1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and in particular to a method using resist patterns each including regularly arranged grooves.
2. Description of the Related Art
In U.S. Pat. No. 5,066,997, a dummy wiring pattern is used to manufacture a memory chip. Furthermore, in general, to manufacture a semiconductor chip having a number of small regularly-arranged elements, such as those of a memory cell array, a pattern having grooves and dummy grooves or consisting of strips and dummy strips has been formed in resist. The grooves or strips are arranged in the central portion of the resist pattern in rows and columns, and separated from each other at a constant distance. The dummy grooves or dummy strips are arranged in a few rows and a few columns, surrounding the grooves or strips. The dummy grooves or dummy strips have the same size and shape as the grooves or strips. They are provided in order to improve the precision of processing the resist. The dummy strips are functional, since the strips are isolated from each other, as shown in FIGS. 1 and 2, which are a plan view and a cross-sectional view, respectively, both showing arrangement of strips 101 formed of resist.
On the other hand, the dummy grooves do not function well for the following reason:
In the resist pattern having grooves, that portion of the resist pattern which surrounds the grooves and the dummy grooves is continuous with that portion of the resist pattern which exists between any two adjacent grooves. Therefore, the latter portion is pulled by the former portion which shrinks as the resist is heated after it has been developed. This disadvantage will be further explained with reference to FIGS. 3, 4A and 4B.
FIG. 3 is a plan view showing a resist pattern having grooves 103 formed in resist 102, and FIG. 4A and 4B are a cross-sectional view of the resist pattern after development and a cross-sectional view of the resist pattern after heat treatment, respectively. As shown in FIG. 3, in the resist 102, a resist portion surrounding the grooves 103 is continuous with resist portions provided between the grooves 103, and has a greater width than each of the resist portions. The resist 102 shrinks as it is heated in order to improve its adhesion. In particular, the surrounding resist portion shrinks considerably, and thus pulls the resist portions as shown in FIG. 4B. Therefore, the resist pattern is deformed even if the dummy grooves are provided. In order to prevent such deformation of the resist pattern, additional dummy grooves must be formed in the resist pattern, inevitably increasing the chip size.